Clemastine

Clemastine
Clemastine
Systematic (IUPAC) name
(2R)-2-{2-[(1R)-1-(4-chlorophenyl)-1-phenylethoxy]ethyl}-1-methylpyrrolidine
Clinical data
Trade names Tavist-1
AHFS/Drugs.com monograph
MedlinePlus a682542
Pregnancy cat. B (USA)
Legal status Unscheduled;
OTC
Routes Oral
Pharmacokinetic data
Bioavailability 39.2%
Metabolism Hepatic
Half-life 21.3 Hours
Excretion Renal
Identifiers
CAS number 15686-51-8 YesY
ATC code R06AA04
PubChem CID 26987
DrugBank APRD00875
ChemSpider 25129 YesY
UNII 95QN29S1ID YesY
KEGG D03535 YesY
ChEBI CHEBI:3738 YesY
ChEMBL CHEMBL1626 YesY
Chemical data
Formula C21H26ClNO 
Mol. mass 343.9
SMILES eMolecules & PubChem
 N(what is this?)  (verify)

Clemastine, also known as meclastin, is an antihistamine and anticholinergic. Unlike loratadine or fexofenadine, clemastine is a sedating antihistamine, however it exhibits fewer other side effects than most of the widely used antihistamines.[citation needed] Clemastine is also classified as an antipruritic (i.e. it stops itching).

Contents

Pharmacology

Clemastine is an antihistamine with anticholinergic and sedative effects. Antihistamines competitively bind to histamine receptor sites, thus reducing the neurotransmitter's effects. Effects of histamine (which are countered by antihistamines) include:

  • Increased capillary permeability
  • Increased capillary dilatation
  • Edema (i.e. swelling)
  • Pruritus (Itch)
  • Gastrointestinal/respiratory smooth muscle constriction

Clemastine inhibits both the vasoconstrictor and vasodilator effects of histamine. Depending on the dose, the drug can produce paradoxical effects, including CNS stimulation or depression.

Most antihistamines exhibit some type of anticholinergic activity. Antihistamines act by competitively binding to H1- receptor sites, thus blocking the binding endogenous histamine. Antihistamines do not chemically inactivate or prevent the normal release of histamine.

Clemastine is rapidly absorbed from the gastrointestinal tract and peak plasma concentrations are attained in 2-4 hours.

Mechanism of Action

Clemastine is a selective histamine H1 antagonist. It binds to the histamine H1 receptor, thus blocking the action of endogenous histamine, which leads to temporary relief of the negative symptoms caused by histamine.

Metabolism

Antihistamines are thought to be metabolized in the liver, mostly by mono-/didemethylation and glucuronide conjugation. It is an inhibitor of cytochrome P450 2D6 and may interfere with other drugs metabolized by this isozyme.

Indications

Clemastine is indicated for use in treating allergic rhinitis, such as sneezing, rhinorrhea, pruritus and lacrimation.

Availability

Clemastine is an OTC drug, and is available as a syrup (0.5 mg per 5mL) and tablet (1mg). It is sold in the United States under the brand name Tavist.

Brand Names in other countries

Brasil - In Brasil it is sold under the brand name of Agasten by Novartis.

Germany - In Germany sold under the brand name Tavegil.

Sweden - In Sweden it is sold under the brand name of Tavegyl and unlike the newer non-sedative antihistamines used for allergy, prescription only.

Turkey - Sold under the brand name Tavegyl by Novartis.

Toxicity

Overdosage symptoms are paradoxical, ranging from CNS depression to stimulation. Stimulation is most common in children, and is usually followed by excitement, hallucinations, ataxia, incoordination, muscle twitching, athetosis, hyperthermia, cyanosis convulsions, tremors, and hyperreflexia. This may be followed by postictal depression and cardiovascular/respiratory arrest. Other common overdose symptoms include dry mouth, fixed dilated pupils, flushing of the face, and pyrexia. In adults, overdose usually leads to CNS depression, ranging from drowsiness to coma.

The oral LD50 of clemastine in the rat and mouse is 3550 mg/kg and 730 mg/kg, respectively.

External links


v · d · eAntipruritics (D04)
Antihistamines for topical use
Anesthetics for topical use

M: INT, SF, LCT

anat/phys/devp

noco(i/b/d/q/u/r/p/m/k/v/f)/cong/tumr(n/e/d), sysi/epon

proc, drug (D2/3/4/5/8/11)

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Look at other dictionaries:

  • clemastine fumarate — the fumarate salt of clemastine, used in the treatment of allergic rhinitis, allergic conjunctivitis, and cutaneous manifestations of allergic reactions, and as an ingredient in some cough and cold preparations; administered orally …   Medical dictionary

  • clemastine — noun A particular sedative antihistamine drug. Syn: meclastin …   Wiktionary

  • clemastine — An H1 antihistaminic. SYN: meclastine. * * * clem·as·tine klem ə .stēn n an antihistamine administered in the form of its fumarate C21H26ClNO·C4H4O4 * * * n. an antihistamine used for the treatment of symptoms of hay fever and urticaria. It is… …   Medical dictionary

  • clemastine — n. an antihistamine used for the treatment of symptoms of hay fever and urticaria. It is administered by mouth; commonest side effects are dizziness, sleepiness, and stomach upset. Trade names: Tavegil …   The new mediacal dictionary

  • clemastine fumarate — /klem euh steen fyooh meuh rayt /, Pharm. an antihistamine, C25H30ClNO5, that has drying and some sedative effects, used for symptomatic relief of allergy. [perh. a rearrangement of meclastine an alternate name, perh. ME(THYL) + C(H)L(ORO) +… …   Universalium

  • clemastine fumarate — /klem euh steen fyooh meuh rayt /, Pharm. an antihistamine, C25H30ClNO5, that has drying and some sedative effects, used for symptomatic relief of allergy. [perh. a rearrangement of meclastine an alternate name, perh. ME(THYL) + C(H)L(ORO) +… …   Useful english dictionary

  • Клемастин (Clemastine) — антигистаминный лекарственный препарат, применяемый для лечения сенной лихорадки, крапивницы и ангионевротического отека; оказывает также высушивающее воздействие на кожу. Назначается внутрь; характерные побочные эффекты: головокружение,… …   Медицинские термины

  • КЛЕМАСТИН — (clemastine) антигистаминный лекарственный препарат, применяемый для лечения сенной лихорадки, крапивницы и ангионевротического отека; оказывает также высушивающее воздействие на кожу. Назначается внутрь; характерные побочные эффекты:… …   Толковый словарь по медицине

  • H1 antagonist — An H1 antagonist is a histamine antagonist of the H1 receptor that serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions. Agents where the main therapeutic effect is… …   Wikipedia

  • Histamine antagonist — A histamine antagonist, commonly referred to as antihistamine, is a pharmaceutical drug that inhibits action of histamine by blocking it from attaching to histamine receptors. Contents 1 Clinical effects 2 Clinical: H1 and H2 receptor antagonists …   Wikipedia

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